Coherent lattice vibration of interlayer shearing mode of graphite

Mishina, Tomobumi; Nitta, Kazuki; Masumoto, Yasuaki

doi:10.1103/physrevb.62.2908

Cited by 57 publications

(63 citation statements)

References 18 publications

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“…Figure 1a shows the fluence dependent transient absorption of graphite at a probe energy of 1.7 eV. At early times, we find a very fast transmission increase ( <40 fs), followed by a bi-exponential decay with an ultrafast component ('200 fs) and a slower one ('2 ps), consistent with previous reports at different energies and fluences [3,6,7]. At high fluence we also observe a modulation of '700 fs, due to an out-of-plane coherent phonon [6,9].…”

Section: Introductionsupporting

confidence: 78%

“…The very low repetition rate of our experiment (500 Hz), compared to previous studies using 5 kHz to MHz repetition rates [3,6,9,7], corresponds to 2 ms between pulses, which allows graphite to dissipate the heat deposited by the intense laser excitation and study its ultrafast optical properties up to the level of permanent damage [16]. The white light continuum probe (1.7-3 eV) was generated in a CaF 2 plate, and directed perpendicular to the graphene layers (c-axis), with the polarization in the graphene planes (ab-plane); the reflected or transmitted signal was recorded on a spectrometer.…”

Section: Introductionmentioning

confidence: 85%

“…Surprisingly, despite years of research, a consensus on the microscopic interpretation of the observed ultrafast dynamics is still lacking. Transient absorption pump-probe studies revealed that the electronic excitation decays in a bi-exponential fashion with an ultrafast ('200 fs) component and a slower (1-2 ps) one [3,6,7]. The latter has been interpreted as a slow electron-hole recombination akin to that of a semiconductor [3].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Femtosecond carrier dynamics in bulk graphite and graphene paper

Carbone

Auböck

Cannizzo

et al. 2011

Chemical Physics Letters

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Section: Introductionsupporting

confidence: 78%

Section: Introductionmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

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Femtosecond carrier dynamics in bulk graphite and graphene paper

Carbone

Auböck

Cannizzo

et al. 2011

Chemical Physics Letters

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“…Previous optical studies have focused on the carrier dynamics induced by both high [10,11] and low fluence [12] optical excitation, revealing features of the unique phonon excitations in quasi-two-dimensional graphite and the coherent modes involved. In order to resolve details of the structure, diffraction is our method of choice.…”

mentioning

confidence: 99%

“…The period of '1 ps reported here is consistent with the c-axis optical phonon frequencies (obtained from inelastic neutron scattering [25]), which cover the range of ÿ1 op ' 0:7-1:4 ps. The observed oscillation in the timeresolved spectra [12] was assigned to a vibration (E 2g ) shear mode (43 cm ÿ1 ), which gives a period of ' 0:8 ps.…”

mentioning

confidence: 99%

Structural Preablation Dynamics of Graphite Observed by Ultrafast Electron Crystallography

Carbone

Baum

Rudolf³

et al. 2008

Phys. Rev. Lett.

143

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By means of time-resolved electron crystallography, we report direct observation of the structural dynamics of graphite, providing new insights into the processes involving coherent lattice motions and ultrafast graphene ablation. When graphite is excited by an ultrashort laser pulse, the excited carriers reach their equilibrium in less then one picosecond by transferring heat to a subset of strongly coupled optical phonons. The time-resolved diffraction data show that on such a time scale the crystal undergoes a contraction whose velocity depends on the excitation fluence. The contraction is followed by a large expansion which, at sufficiently high fluence, leads to the ablation of entire graphene layers, as recently predicted theoretically. DOI: 10.1103/PhysRevLett.100.035501 PACS numbers: 61.82.ÿd, 07.78.+s, 63.20.Kÿ, 78.47.ÿp The unique semimetal physical properties of graphite and its chemical inertness make possible numerous applications [1][2][3] including the use in nuclear reactors [4,5]. When subjected to a shock, the structure distorts, and the ablation to form graphene [6] may result from its instability. It is of fundamental importance to visualize the associated dynamics with atomic-scale spatial and temporal resolutions. Here, by means of ultrafast electron crystallography, we report direct observation of the structural dynamics of graphite following an impulsive near infrared excitation. The diffraction shows that the structure of graphite first contracts perpendicular to the layer planes on the time scale of 0.5 to 3 ps, depending on fluence, and then nonthermally expands in 7 ps. The excitation fluence dependence of both processes indicates a distinct behavior. The highly anisotropic transfer of carrier energy to a subset of phonons of the quasi-2D-structure alters the forces between layers which control the time scale and amplitude of structural change. These atomic motions on different time scales for compression, expansion and restructuring determine the degree of the instability, which at sufficiently high fluences reaches that of graphene ablation [7,8], as predicted theoretically [9].Previous optical studies have focused on the carrier dynamics induced by both high [10,11] and low fluence [12] optical excitation, revealing features of the unique phonon excitations in quasi-two-dimensional graphite and the coherent modes involved. In order to resolve details of the structure, diffraction is our method of choice. In ultrafast electron crystallography, the probing wavelength is 0.07 Å at 30 keV electron acceleration energy, and we use femtosecond (fs) near infrared pulses (800 nm) for the optical excitation of the system of graphite. The overall resolution is determined by group velocity mismatch [13], but as shown here, by tilting the optical wave front, see the inset in Fig. 4, we are able to resolve subpicosecond coherent dynamics. Highly oriented and single crystal graphite were studied, and indeed the static diffraction patterns of both display the characteristic structural features...

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Excitation and Time‐Evolution of Coherent Optical Phonons

Hase

Misochko

Ishioka

2010

Dynamics at Solid State Surfaces and Interfaces

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Coherent optical phonons are the lattice vibrations of the optical branches excited in-phase over a macroscopic spatial region by ultrashort laser pulses. Their generation and relaxation dynamics have been investigated by optical pump-probe techniques in a broad range of solid materials. When probed with a linear optical process such as reflection, the probing depth is from nanometers to micrometers determined by the absorption coefficient and the laser wavelength. By employing a nonlinear optical process such as second harmonic generation, however, it is possible to monitor coherent phonons at surfaces and interfaces exclusively. When the photoexcitation creates electron-hole plasma, coherent phonons can also serve as an ultrafast probe of nonequilibrium electron-phonon coupling. Using an optical pulse train with a designed repetition rate, coherent phonons can be excited to large amplitudes, which is expected to be a promising strategy toward nonthermal phase transitions in solids. New femtosecond beam sources such as X-ray and THz pulses offer complementary techniques to probe the ultrafast phononic and electronic dynamics under extremely nonequilibrium conditions. Coherent Phonons in Group V SemimetalsBismuth (Bi) and antimony (Sb) have been model systems for optical studies on coherent phonons because of their relatively low frequencies and large amplitudes in the optical reflectivity. They both have an A7 crystalline structure and sustain two Raman-active optical phonon modes shown in Figure 10.1e. The coherent phonons of A 1g and E g symmetries have been detected as periodic modulations of the reflectivity (Figure 10.1a) in the order of DR=R¼ 10 À6 to 10 À2 depending on the excitation density. Recently, the coherent A 1g phonons of Bi have gained a renewed interest as the benchmark for femtosecond X-ray diffraction experiments.

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Coherent lattice vibration of interlayer shearing mode of graphite

Cited by 57 publications

References 18 publications

Femtosecond carrier dynamics in bulk graphite and graphene paper

Femtosecond carrier dynamics in bulk graphite and graphene paper

Structural Preablation Dynamics of Graphite Observed by Ultrafast Electron Crystallography

Excitation and Time‐Evolution of Coherent Optical Phonons

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